The Duke of Cambridge is deferring taking on royal engagements full-time to return to his love of flying to become an air ambulance pilot.

Kensington Palace said William planned to join the East Anglian air ambulance (EAAA), based at Cambridge airport, next spring. He will begin a civilian pilot course next month in preparation, followed by dedicated 999-response training.

The announcement confirms rumours rife since the duke ended active service as an RAF search and rescue pilot in September last year. The full-time role, for which he will donate his salary to charity, will be fitted in around royal duties.

He will sign an employment contract with a civilian employer (Bond Air Services) and is believed to be the first member of the royal family in direct succession to do so.

The job is convenient for the Cambridges' new country home, Anmer Hall, a Grade II-listed 10-bedroom mansion on the Queen's Sandringham estate, recently privately refurbished to accommodate the duke and duchess and Prince George.

While in London, the couple will reside at their 21-room apartment at Kensington Palace, recently refurbished at a cost of £4.5m to the public purse.

A Kensington Palace spokesman said William, 32, was "very much looking forward to" the next step in his career.

The EAAA operates two helicopters and employs three pilots in Norwich and three in Cambridge, covering Norfolk, Suffolk, Cambridgeshire and Bedfordshire. Along with a pilot, each helicopter carries a doctor and a paramedic.

William's main duties will involve flying an EC145 T2 aircraft, working alongside medics to respond to emergencies ranging from road accidents to heart attacks.

Patrick Peal, chief executive of the EAAA, said the organisation would benefit both from William's skills as a pilot and from a boost to the charity's profile.

"We're very fortunate that we currently enjoy tremendous levels of support, but fundraising is always a challenge – we're looking to raise £7.5m a year to continue the lifesaving work – and I'm sure that this will help to raise the profile of the charity. We're looking forward to him being part of the team," he said.

Alastair Wilson, the charity's medical director, said he felt the duke was well-suited to the role. "Compared to his role as a search and rescue pilot, he may be dealing with more injury patients than he is used to, but I'm sure he will adapt very well to that."

Before beginning the job, William will be required to gain an air transport pilot licence to complement his military training, and to undergo training specific to his new role. In order to gain the licence, he must complete five months of training followed by 14 exams and a flight test.

Initially he will be employed as a co-pilot, but after a period of training he will be qualified as a helicopter commander.

A palace spokesman said: "The job will build on the duke's operational experience in the Royal Air Force search and rescue force. During this time he undertook more than 150 search and rescue operations."

This year William completed a 10-week bespoke agricultural course at the University of Cambridge designed to help him run the Duchy of Cornwall, which he will inherit and which will provide a generous income for him on becoming Prince of Wales.